1. Field of the Invention
This invention relates to a tool for turning large diameter objects in limited work areas and more particularly relates to the turning of a large nut used on petroleum coking equipment.
2. Description of the Prior Art
Delayed coking is a well-known process. Typically, each coker comprises a vertically-oriented cylindrical drum. The drum has a top head and a bottom head covering and sealing the top and bottom, respectively, of the drum. The drum is a massive vessel, typically about twenty-six feet in diameter and about eighty-six feet tall. The top head and the bottom head also are massive devices, being about six feet in diameter and each weighing approximately two and one-half tons.
Heavy liquid hydrocarbon feed to the coker typically is preheated in a heater to a temperature in the range of about 700.degree. to 900.degree. F. The feedstream is thermally cracked in the coke drum for an extended period of time during the coking cycle to produce gas and gas oil and other hydrocarbon product streams of various boiling ranges and to form porous carbonaceous petroleum coke. The gas and normally liquid product streams are removed as vapors during the coking cycle from the top of the drum, and the coke remains in the drum at the end of the coking cycle. The hydrocarbon feed is switched from the coke drum to a second parallel coke drum while the first drum is taken off-line, and coke is removed from the first drum.
Hydrocarbon feed to each coker is typically fed to the on-line coke drum through an inlet port which is typically incorporated into the drum bottom head, and product vapor streams exit the vessel through process an outlet port, which is typically incorporated in the top head.
The coke is then cleaned using steam to remove any entrained hydrocarbons and is cooled with water. To remove the coke from the off-line drum, the top and bottom heads of the drum must be removed. After both the top and bottom heads and the chute cover are removed, the coke in the drum is cut by a hydraulic water jets using, for example, a 3000 psi water rotating water drill. First, a vertical pilot hole is drilled through the core of the coke to provide a channel for coke discharge through the bottom opening of the coke drum. Then, the water drill is directed against the upper surface of the coke at a distance from the central discharge core and cuts the coke into pieces, which pieces fall out of the drum, and through the pilot hole. The water drill jet is moved in both a circular and vertical pattern until all of the coke is cut and falls from the drum into a discharge chute and then on to coke storage.
In order to change from the coking where hydrocarbons exit the top of the coker drum, to the drilling mode where the drill stem is positioned over the top of the coker drum, a coker drill stem must be swung to the top of the coker. A gearbox is used to swing the coker drill stem. The gearbox swivel assembly has a large nut, approximately eleven inches in diameter having several holes in its outer diameter capable of receiving a pin. The maintenance and repair requirements for the gearbox swivel assembly require the removal and replacement of the nut. The nut is located a limited area between several upright members on the assembly.
In the past, this large nut has required two people using a large spanner wrench and a mallet to apply the necessary torque. The spanner was fit around the nut and its pin fit into one of the holes on the nut. The first person held the spanner while the second pounded the spanner with a mallet. This method is labor intensive, time consuming and difficult in the limited area available because the wrench must be moved to several times around the circumference of the nut to turn it. In addition, it required two people and its physical location made it difficult to work on safely. There is a need for a simple and effective means for one person to safely apply the torque needed to turn this large nut in the limited area available.